Method and device for supporting access of point to point protocol over ATM terminal

ABSTRACT

A method for supporting access of a Point to Point Protocol over Asynchronous Transfer Mode (PPPoA) terminal including: the PPPoA terminal initiates a Point to Point Protocol (PPP) negotiation to a broadband access device based on an Internet Protocol (IP) architecture; the broadband access device assigns a Media Access Control (MAC) address to the PPPoA terminal, builds a Point to Point Protocol over Ethernet (PPPoE) connection between itself and a Broadband Access Server (BAS) and acquires a Session ID; the broadband access device converts a PPPoA packet sent by the PPPoA terminal into a PPPoE packet and sends the PPPoE packet to the BAS according to the MAC address and Session ID, and converts the PPPoE packet sent by the BAS into the PPPoA packet and sends the PPPoA packet to the PPPoA terminal. A device for supporting the access of a PPPoA terminal is provided.

This application is a continuation of International Patent ApplicationNo. PCT/CN2005/001085, filed Jul. 20, 2005, which claims priority toChinese Patent Application No. 200410069585.9, filed Jul. 20, 2004, allof which are hereby incorporated by reference.

FIELD OF THE TECHNOLOGY

The present invention relates to access technologies in communicationnetworks, and more particularly, to a method and device for supportingaccess of Point to Point Protocol over an Asynchronous Transfer Mode(ATM) terminal.

BACKGROUND OF THE INVENTION

In broadband access networks, besides a Point to Point Protocol overEthernet (PPPoE) mode based on Ethernet, a Virtual Local Area Network(VLAN) mode and an 802.1 x authentication mode which are very popular atpresent, a Point to Point Protocol over ATM (PPPoA) mode has been usedall along. In the PPPoA access mode, a Point to Point Protocol (PPP)call is initiated by a PPPoA terminal, and a series of PPP accessprocedures, such as authorization, authentication, Internet Protocol(IP) address assignment and charging, are performed by an ATM BroadbandAccess Server (BAS). As shown in FIG. 1, the specific steps are asfollows:

Step 101: A PPPoA terminal initiates a PPP negotiation to the ATM BASdevice, the PPPoA terminal performs a PPP Link Control Protocol (LCP)negotiation with the ATM BAS device to configure and test data links.The PPPoA packet is terminated in the ATM BAS device. The ATM BAS devicecontrols the LCP negotiation procedure, analyzes the PPPoA packet andresponds to the PPPoA terminal to complete the LCP negotiationprocedure. The controlling methods of negotiation procedures describedhereinafter are the same.

Step 102: Based on the result of the LCP negotiation, whether to adopt aPassword Authentication Protocol (PAP) or a Challenge-HandshakeAuthentication Protocol (CHAP) in the authentication procedure isdetermined. After the LCP negotiation, the PAP or the CHAPauthentication procedure starts.

Step 103: After the authentication procedure and the PPPoA terminalpasses the authentication, a link is built. The PPPoA terminal performsa PPP Network Control Protocol (NCP) negotiation with the ATM BAS deviceto choose and configure one or more network layer protocols, and to getauthorization instruction of the PPPoA terminal. Then the PPPnegotiation is completed. At the same time, the ATM BAS device startscharging for the PPPoA terminal.

Step 104˜Step 105: The PPPoA terminal accesses the Internet, meanwhile,the ATM BAS device terminates the PPPoA packets sent by the PPPoAterminal, that is, removes the protocol headers of the PPPoA packets,extracts the data from the PPPoA packets, and sends the data to theInternet. The extracted data from the PPPoA packets by the ATM BASdevice are the specific data contents sent by the PPPoA terminal to theInternet.

Step 106: The PPPoA terminal logs off and notifies the ATM BAS device,the ATM BAS device stops charging for the PPPoA terminal and terminatesthe access to the Internet of the PPPoA terminal.

The Ethernet achieves a great success by equally super fast transmissionrate and lower networking cost than the ATM along with development ofthe Ethernet technology. ATM Digital Subscriber Line Access Multiplexer(DSLAM) devices start to convert to IP DSLAM devices, and the IP DSLAMdevices with more and more powerful functions are adopted in networkupgrading.

There are mainly two forms in the existing DSLAM access devices: an ATMDSLAM and an IP DSLAM, where the ATM DSLAM device is a broadband accessdevice whose core is an ATM switch while the IP DSLAM device is abroadband access device whose core is a switch based on the combinationof VLAN and Media Access Control (MAC). Broadband access devices can beclassified into two categories, that is, frame type and box type, interms of the device forms, and as shown in FIG. 2, devices of bothcategories include four components: a main control functional module, aswitching functional module, a subscriber interface functional moduleand a backplane functional module. The subscriber interface functionalmodule is used for providing access interfaces for subscribers, anddifferent subscriber interface functional modules can provide differentaccess methods such as an Asymmetric Digital Subscriber Line (ADSL), aVery High Data Rate Digital Subscriber Line (VDSL), an Ethernet, and aSymmetric High Data Rate Digital Subscriber Line (G.SHDSL). Typically,one broadband access device can provide multiple subscriber interfacefunctional modules, and the subscriber interface functional modules arenumbered by a slot number, starting from 0 or 1. Multiple lineinterfaces for subscriber to access such as 16, 24, or 48 interfaces canbe provided in one subscriber interface functional module, and theseinterfaces are numbered uniformly, starting from 0 or 1. The maincontrol functional module is used for implementing control andadministration functions of the broadband access device. The switchingfunctional module is used for implementing traffic converting andprocessing functions of the whole broadband access device, and forimplementing an interface of the network side. The backplane functionalmodule is used for providing connection and communication functions forthe above functional modules.

The broadband access device based on the ATM core is one generation ofcurrent mainstream type of access device. The broadband access deviceadopts a switching structure of ATM, that is, both data communicationbetween the subscriber interface functional module and the main controlfunctional module, and the data communication between the subscriberinterface functional module and the switching functional module use theATM bearer, adopting a shared cell bus or an ATM bus interface. At thesame time, the switching subsystem is also based on switches of the ATMcells. As shown in FIG. 3A, the specific service procedure is asfollows: service data are transmitted from the subscriber interfacefunctional module to the switching functional module by an ATM VirtualChannel (VC) bearer and the cell based bus of the backplane functionalmodule, the switching functional module forwards the service data usinga cell based switching method, that is, performs a Virtual PathIdentifier (VPI)/Virtual Channel Identifier (VCI) conversion of the ATMVC header, and outputs the service data to a corresponding output port.

Because the ATM technology has stopped developing, the ATM interfacebandwidth of mainstream applications has stops at the level of STM-1,155 Mbps, the bandwidth capacity of STM-4, 622 Mbps and the bandwidthcapacity of STM-16, 2.5 Gbps have not been used commercially because oftoo high interface costs. Meanwhile, demands for the network bandwidthincreasingly rise with development of various network services, and theATM switching network has been unable to meet the demands for largerbandwidth. Mainstream services in networks are now using the IP bearerwhile the ATM is based on a connection mode. Therefore, the ATM cannoteffectively perceive the multiple services on the IP bearer, and thus,cannot effectively guarantee the quality of multiple services. When itcomes with an IP Television (IPTV) service, which is a multicast videoservice of mainstream applications, because of the technicalcharacteristic of a point to point connection of the ATM, configurationand maintenance administration for such a point to multiple pointsservice is rather complex, thus, no commercial network can be builteffectively, which makes it impossible to support the development ofsuch mainstream services with the ATM.

As the bandwidth of the ATM core based broadband access device is small,an Ethernet/IP core based broadband access device, which is relatively anew broadband access device at present, is proposed. Because an EthernetLayer 2(L2)/Layer 3(L3) based switching structure is adopted by an IPbroadband access device, a larger switching capability such as 10Gbps—48 Gbps or even larger can be provided, and also an interfacebandwidth of Fast Ethernet (FE)/Gigabit Ethernet (GE), even 10 GE, canbe provided. Thus, the bottleneck of bandwidth is resolved. Both thedata communication between the subscriber interface functional moduleand the main control functional module and the data communicationbetween the subscriber interface functional module and the switchingfunctional module are born by the Ethernet, and an FE or a GE connectioncan be adopted between the subscriber interface functional module andthe main control functional module while the switching functional modulewitches based on the Ethernet. As shown in FIG. 3B, the specific serviceprocedure is as follows:

a service accessed by the subscriber interface functional module iscarried by the ATM VC bearer or the Ethernet bearer, and the subscriberinterface functional module reorganizes and restores the ATM cells to anEthernet packet, adds an 802.1Q based VLAN identifier to the Ethernetpacket, and then transmits it to the switching functional module by anEthernet based FE/GE star style bus of the backplane functional module.Then, the switching system forwards the service data based on aswitching method combining the VLAN and the MAC addresses or based onthe IP addresses, and outputs the service data to a corresponding outputport.

Thus, how to support a PPPoA based access method on the IP DSLAM devicebecomes an urgent problem to be solved.

SUMMARY OF THE INVENTION

A method for supporting the access of a Point to Point Protocol overAsynchronous Transfer Mode (PPPoA) terminal is provided by the presentinvention, and a device for supporting the access of a PPPoA terminal isalso provided.

The method provided by the invention for supporting access of a PPPoAterminal to a broadband access device which is based on the IParchitecture includes the following steps:

assigning, by the broadband access device, a Media Access Control (MAC)address to the PPPoA terminal;

setting up a Point to Point Protocol over Ethernet (PPPoE) connectionbetween the broadband access device and a Broadband Access Server (BAS),and acquiring, by the broadband access device, a Session ID assigned bythe BAS;

converting, by the broadband access device, a PPPoA packet sent by thePPPoA terminal into a PPPoE packet and sending the PPPoE packet to theBAS, and converting, by the broadband access device, the PPPoE packetsent by the BAS into the PPPoA packet and sending the PPPoA packet tothe PPPoA terminal according to the MAC address and the Session ID.

A device for supporting access of a Point to Point Protocol overAsynchronous Transfer Mode (PPPoA) terminal, including a main controlfunctional module, a switching functional module, a subscriber interfacefunctional module and a backplane functional module, and

a conversion functional module, used for converting a PPPoA packet sentby the PPPoA terminal into a Point to Point Protocol over Ethernet(PPPoE) packet and sending the PPPoE packet to an Ethernet BAS device,as well as converting the PPPoE packet sent by an Ethernet BroadbandAccess Server (BAS) device into the PPPoA packet and sending the PPPoApacket to a PPPoA terminal.

An accessing system for supporting a Point to Point Protocol overAsynchronous Transfer Mode (PPPoA) terminal, includes an InternetProtocol (IP) architecture based broadband access device and a BroadbandAccess Server (BAS);

the broadband access device is used for assigning a Media Access Control(MAC) address to a PPPoA terminal, setting up a Point to Point Protocolover Ethernet (PPPoE) connection between the BAS and itself, convertinga PPPoA packet sent by the PPPoA terminal into a PPPoE packet andsending the converted PPPoE packet to the BAS, and converting a PPPoEpacket sent by the BAS into a PPPoA packet and sending the PPPoA packetto the PPPoA terminal, according to the MAC address and a session ID;

the BAS is used for assigning the session ID to the broadband accessdevice.

According to embodiments of the present invention, a broadband accessdevice such as an IP DSLAM device is able to convert PPPoA packets andPPPoE packets into each other, which enables a PPPoA terminal to accessa broadband network via an IP architecture based broadband accessdevice, that is, access the broadband network via a broadband accessdevice in the Ethernet mode, and enables the broadband access device tocooperate with a standard BAS such as an Ethernet BAS device withoutspecial processing and to be connected to all BAS conveniently.Additionally, abnormal logoff of a PPPoA terminal could be detected withan effective method in the implementing procedure in accordance with anembodiment of the present invention, which guarantees the inter-workingcapability of the protocol. Therefore, accesses of PPPoA terminal can besupported well in a broadband access device and network resources can besaved efficiently. Thus, in accordance with embodiments of the presentinvention, the compatibility of the network for existing ATM networksubscribers is extended and the work in network reconstruction byoperators is reduced.

Furthermore, the MAC address resources can be saved efficiently bymanaging the MAC addresses of PPPoA terminals dynamically by thebroadband access device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a flow chart of a PPPoA terminal accessing a broadbandnetwork in the prior art;

FIG. 2 shows a schematic diagram of the structure of an existingbroadband access device;

FIG. 3A shows a schematic diagram of data transmission in an ATM DSLAMdevice;

FIG. 3B shows a schematic diagram of data transmission in an IP DSLAMdevice;

FIG. 4 shows a schematic diagram of networking that supports both thePPPoA terminals and the PPPoE terminals on an IP DSLAM device inaccordance with an embodiment of the present invention;

FIG. 5 shows a flow chart of a PPPoA terminal accessing a broadbandnetwork via an IP DSLAM device in accordance with an embodiment of thepresent invention;

FIG. 6 shows a schematic diagram of converting data in the link layer inaccordance with an embodiment of the present invention;

FIG. 7 shows a flow chart of processing the logoff of a PPPoA terminalin accordance with an embodiment of the present invention;

FIG. 8 shows a schematic diagram of the structure of a broadband accessdevice in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Because the IP DSLAM device mainly supports the PPPoE access method andthe core of the IP DSLAM adopts an Ethernet based switching core,existing PPPoA terminals cannot access a broadband network via an IPDSLAM device. However, operators do not want to change the using habitsand terminal software of the subscribers. Furthermore, such changes notonly need a great deal of work, but also generate a high cost. As aresult, a fixed mapping method is proposed, in which the PPPoA packetsare converted into the PPPoE packets, enabling the PPPoA terminal toaccess the broadband network by the IP DSLAM device. However, the fixedmapping method has a special requirement on the Ethernet BAS device,that is, requiring that the Ethernet HAS device make a specialprocessing of the PPPoE packets converted from the PPPoA packets.Furthermore, the Ethernet BAS device will enter the Session stagedirectly without building a PPPoE Discovery stage.

The invention is hereinafter described in detail with reference to theembodiments and the accompanying drawings.

In the embodiments of the present invention, PPPoA packets and PPPoEpackets are converted into each other in the broadband access device,that is, an IP DSLAM device, so as to enable a PPPoA terminal to accessa broadband network via the IP DSLAM device.

FIG. 4 shows a schematic diagram of networking that supports the PPPoAterminals and the PPPoE terminals on an IP DSLAM device in accordancewith an embodiment of the present invention. As shown in FIG. 4,terminals (that is, PCs shown in the Figure) access a BAS device (thatis, the Ethernet BAS device shown in the Figure) via broadband accessdevices (that is, the IP DSLAM devices shown in the Figure). Theterminals that access the broadband network via the IP DSLAM devicesinclude the PPPoA terminals and the PPPoE terminals.

Packets between the PPPoA terminals and the IP DSLAM devices adopt theencapsulating format of an ATM cell while packets between the IP DSLAMdevices and the Ethernet HAS devices adopt the encapsulating format ofthe PPPoE. A MAC address pool, which is used for the PPPoA terminals, isconfigured for the PPPoA terminals in the IP DSLAM devices in advance,and the IP DSLAM device assigns dynamically or specifies statically aMAC address for a PPPoA terminal from the MAC address pool. The IP DSLAMdevice distinguishes a PPPoA terminal from a PPPoE terminal by the MACaddress pool configured in advance, that is, if the MAC address of aterminal is a MAC address in the MAC address pool configured in advance,the terminal is a PPPoA terminal; if the MAC address of a terminal isnot in the MAC address pool configured in advance, the terminal is aPPPoE terminal. When the IP DSLAM device assigns a MAC address to aPPPoA terminal, it may assign different MAC addresses to different PPPoAterminals, that is, one MAC address corresponds to one PPPoA terminal;or the IP DSLAM device may assign one MAC address to multiple PPPoAterminals, that is, one MAC address corresponds to multiple PPPoAterminals.

FIG. 5 shows a flow chart of a PPPoA terminal accessing a broadbandnetwork by an IP DSLAM device in accordance with an embodiment of thepresent invention. As shown in FIG. 5, the procedure of a PPPoA terminalaccessing the broadband network via an IP DSLAM device includes thefollowing steps:

Step 501; the PPPoA terminal initiates a PPP negotiation to the IP DSLAMdevice when the IP DSLAM device detects that the packet sent by thePPPoA terminal is a PPPoA packet.

Step 502: the IP DSLAM device saves the PPPoA LCP packet sent by thePPPoA terminal and assigns a MAC address to the PPPoA terminal from theMAC address pool configured in advance. The IP DSLAM device may assignthe MAC address to the PPPoA terminal by using a static fixed assigningmethod; or assign the MAC address to the PPPoA terminal by using adynamic method such as assigning in turn.

Step 503 to Step 504; the IP DSLAM device starts a PPPoA sessionprocedure between itself and the Ethernet BAS device and sends a PPPoEActive Discovery Initiation (PADI) packet carrying the MAC address ofthe PPPoA terminal to the Ethernet BAS device; upon receiving the PADIpacket, the Ethernet BAS device returns a PPPoE Active Discovery Offer(PADO) packet to the IP DSLAM device.

Step 505 to Step 506: upon receiving the PADO packet, the IP DSLAMdevice sends a PPPoE Active Discovery Request (PADR) packet to theEthernet BAS device; upon receiving the PADR packet, the Ethernet BASdevice assigns a Session ID for the current session and returns a PPPoEActive Discovery Session-confirmation (PADS) packet carrying the SessionID to the IP DSLAM device. Thus, a session connection between the IPDSLAM device and the Ethernet BAS device is built.

Step 507: the IP DSLAM device sends the saved PPP LCP packet to theEthernet BAS device by the PPPoE session, so as to complete the LCPnegotiation stage between the PPPoA client and the BAS device to set andtest the data link. The PPPoA terminal performs the PAP or the CHAPauthentication procedure with the Ethernet BAS device, and whether toadopt the PAP or the CHAP in the authentication procedure depends on theresult of the LCP negotiation.

Step 508: When the authentication procedure ends and the PPPoA terminalpasses the authentication, a link is built. The PPPoA terminal performsa PPP NCP negotiation stage with the Ethernet BAS device to choose andset one or more network layer protocols, and to get the authorizationinformation of the PPPoA terminal. The PPP negotiation is completed, andat the same time, the Ethernet BAS device starts charging for the PPPoAterminal.

According to the above procedures, a PPP connection between the PPPoAterminal and the Ethernet BAS device is built and a PPPoE connectionbetween the IP DSLAM device and the Ethernet BAS device is built. The IPDSLAM device is used for taking charge of the bottom layer transmissionconnection of the PPP connection between the PPPoA terminal and theEthernet BAS device, that is, the IP DSLAM device converts the PPPoApackets sent by the PPPoA terminal into the PPPoE packets and sends thePPPoE packets to the Ethernet BAS device, and converts the PPPoE packetssent by the Ethernet BAS device into the PPPoA packets and sends thePPPoA packets to the PPPoA terminal.

Step 509: the PPPoA terminal accesses the broadband network, andtransmits data between itself and the Ethernet BAS device through the IPDSLAM device, that is, the IP DSLAM device performs the datatransmission after converting the uplink and the downlink packetsaccording to the set Session ID and the MAC address assigned to thePPPoA terminal. Specifically, when the data are transmitted in theuplink direction, the IP DSLAM device converts the PPPoA packet sent bythe PPPoA terminal into the PPPoE packet and sends the PPPoE packet tothe Ethernet BAS device, upon receiving the PPPoE packet, the EthernetBAS device terminates the PPPoE packet and analyzes the PPPoE packet toobtain the IP packet, and sends the IP packet to the broadband network;when the data are transmitted in the downlink direction, the IP DSLAMdevice receives the PPPoE packet sent by the Ethernet BAS device, andconverts the PPPoE packet into the PPPoA packet and sends the PPPoApacket to the PPPoA terminal after determining that the terminal toreceive the data is a PPPoA terminal according to the MAC address in thePPPoE packet.

When the data are transmitted in the downlink direction, the IP DSLAMdevice determines whether the terminal is a PPPoA terminal or a PPPoEterminal according to the MAC address in the PPPoE packet sent by theEthernet BAS device.

If the terminal is a PPPoA terminal, the IP DSLAM device converts thePPPoE packet into the PPPoA packet according to the destination MACaddress and the Session ID in the PPPoE packet, and sends the PPPoApacket to the specified PPPoA terminal. If the terminal is a PPPoEterminal, the IP DSLAM device sends the PPPoE packet to the PPPoEterminal directly.

If the IP DSLAM device assigns different MAC addresses to differentPPPoA terminals, the different PPPoA terminals can be distinguished bythe MAC addresses, and the IP DSLAM device sends the converted PPPoApackets to the PPPoA terminal corresponding to the MAC address when thedata are transmitted in the downlink direction, if the IP DSLAM deviceassigns the same MAC address to different PPPoA terminals, the differentPPPoA terminals can be distinguished by combination of the MAC addressand the Session ID, and the IP DSLAM device sends the converted PPPoApacket to the PPPoA terminal corresponding to the MAC address and theSession ID when the data are transmitted in the downlink direction

Step 510: the PPPoA terminal logs off and notifies the Ethernet BASdevice, the Ethernet BAS device stops charging for the PPPoA terminaland terminates the accesses to the broadband network of the PPPoAterminal.

The specific data conversion procedure is as follows: when the data aretransmitted in the uplink direction, that is, from a PPPoA terminal tothe Ethernet BAS device, the packet conversion procedure performed bythe IP DSLAM device after the IP DSLAM device receives a packet sent bythe PPPoA terminal is mainly as follows:

(1) upon determining that the packet sent by the terminal is a PPPoApacket, the IP DSLAM device terminates the ATM connection and analyzesthe PPPoA packet to get the PPP load, that is, the data to betransmitted;

(2) the IP DSLAM device generates a PPPoE packet header according to therelated information such as the Session ID, length of the PPP load, andVLAN identifier. For example, the information in a PPPoE packet headermay be filled in as follows: type of the Ethernet, filled in with x8864;version number of the PPPoE protocol, filled in with 0x1; type of thePPPoE protocol, filled in with 0x1; type of the PPPoE packet, filled inwith 0x00 because what is encapsulated in the packet is a PPP packet;Session ID, filled in with the Session ID generated in Step 505 to Step506; length of the session, filled in with the length of the PPP load inthe PPPoA packet.

(3) the IP DSLAM device encapsulates the PPPoE packet header and the PPPload into a PPPoE packet, in which the destination MAC address is theMAC address of the Ethernet BAS device and the source MAC address is theMAC address assigned to the PPPoA terminal in Step 502, and sends thePPPoE packet to the Ethernet BAS device.

When the data are transmitted in the downlink direction, that is, froman Ethernet BAS device to a PPPoA terminal, the packet conversionprocedure that is performed by the IP DSLAM device after the IP DSLAMdevice receives a packet sent by the Ethernet BAS device is mainly asfollows:

(1) upon determining that the terminal is a PPPoA terminal according tothe information such as the MAC address or the VLAN identifier, the IPDSLAM device regenerates the related information such as a PermanentVirtual Circuit (PVC), a port number and a slot number corresponding tothe PPPoA terminal according to the related information such as theSession ID, the MAC address and the VLAN identifier in the PPPoE packet.

(2) the IP DSLAM device analyzes the PPPoE packet to get the PPP load,that is, the data to be transmitted;

(3) the IP DSLAM device encapsulates the PPP load and the relatedinformation to a PPPoA packet and sends the PPPoA packet to the PPPoAterminal.

Data communication between the PPPoA terminal and the broadband networkvia the IP DSLAM device is implemented according to the above describedpacket conversions that are performed by the IP DSLAM device when dataare transmitted in the uplink and downlink directions.

FIG. 6 shows a schematic diagram of converting data in the link layer inaccordance with an embodiment of the present invention. As shown in FIG.6, when data are transmitted in the uplink direction, after passing theIP DSLAM device, the bearer of PPP data changes from the PPPoA layer tothe PPPoE layer; when data are transmitted in the downlink direction,after passing the IP DSLAM device, the bearer of PPP data changes fromthe PPPoE layer to the PPPoA layer.

In the implementing procedure of a PPPoA terminal accessing a broadbandnetwork by an IP DSLAM device in accordance with an embodiment of thepresent invention, a method is also proposed for detecting abnormallogoff of the PPPoA terminal, which makes it possible to effectivelysave the network resources.

FIG. 7 shows the flow chart for processing the logoff of a PPPoAterminal in accordance with an embodiment of the present invention. Asshown in FIG. 7, the procedure for processing a normal logoff of a PPPoAterminal includes the following steps:

Step 701A to Step 704A: the PPPoA terminal sends an LCP logoff requestpacket to the Ethernet BAS device when the PPPoA terminal logs offnormally in the case such as not needing to access the broadband networkany longer; the Ethernet BAS device removes the PPP connection betweenitself and the PPPoA terminal.

Step 705A: the Ethernet BAS device sends a PPPoE logoff packet to the IPDSLAM device to instruct the IP DSLAM device to remove the PPPoEconnection between the IP DSLAM device and the Ethernet BAS device, theEthernet BAS device stops charging for the PPPoA terminal, and removesthe PPPoE connection between itself and the IP DSLAM device. Uponreceiving the PPPoE logoff packet, the IP DSLAM device removes the PPPoEconnection between itself and the Ethernet BAS device.

After the PPP connection between the Ethernet BAS device and the PPPoAterminal is built, the PPPoA terminal and the Ethernet BAS device keepsending LCP packets as keep alive packets to each other via the IP DSLAMdevice periodically, such as every 15 seconds. The IP DSLAM devicetransparent transmits the LCP packet without any processing of the LCPpacket. According to the PPP protocol, the PPP connection between theEthernet BAS device and the PPPoA terminal will be removed if there isno response after sending the LCP packet for three times. Therefore,after the connection between the Ethernet BAS device and the PPPoAterminal is built, the IP DSLAM device can keep counting the number ofthe LCP packets for maintaining the PPP link layer and detectsperiodically, such as every one minute, whether the number of the LCPpackets periodically increases. If the number of the LCP packetsperiodically increases, it means that the connection between the PPPoAterminal and the IP DSLAM device is normal, the timer is to berestarted; otherwise, it means that a failure may occurs in theconnection between the PPPoA terminal and the IP DSLAM device, the timeris restarted and detects whether the number of the LCP packets changesin the period. If the number of the LCP packets has been detected to beunchanged for n times, where n may be 2, 3, 4, and etc, the IP DSLAMdevice determines that the PPPoA terminal has logged off and theconnection between itself and the PPPoA terminal has been removed. Sothe IP DSLAM device sends a request initiatively to the Ethernet BASdevice to remove the PPPoE connection. Alternatively, a method ofdetecting whether the data traffic between the PPPoA terminal and theEthernet BAS device, that is, data traffic of the correspondingconnection, changes in a set time period may be adopted to determinewhether the connection is kept.

The procedure for processing an abnormal logoff of a PPPoA terminalincludes the following steps:

Step 701B: the IP DSLAM device detects that the number of the LCPpackets or data traffic of the connection does not increase in ncontinuous periods of set time.

Step 702B: the IP DSLAM device sends a PPPoE logoff packet to theEthernet BAS device and the Ethernet BAS device removes the PPPoEconnection between itself and the IP DSLAM device after receiving thePPPoE logoff packet.

After the PPPoA terminal logs off, the IP DSLAM device can return theMAC address assigned to the PPPoA terminal to the MAC address pool, soas to enable the MAC address to be assigned to other PPPoA terminal. ThePPPoA terminal herein includes the PPPoA terminal logged off normallyand the PPPoA terminal logged off abnormally.

FIG. 8 shows a schematic diagram of the structure of a broadband accessdevice in accordance with an embodiment of the present invention. Asshown in FIG. 8, the broadband access device includes an main controlfunctional module, a switching functional module, a subscriber interfacefunctional module and a backplane functional module, and furtherincludes a conversion functional module, which is used for receivingpackets sent by a terminal or broadband access server such as anEthernet BAS device and converting a PPPoA packet and a PPPoE packetinto each other, that is, used for converting the PPPoA packet sent by aPPPoA terminal into a PPPoE packet and sending the PPPoE packet to theEthernet BAS device, and used for converting the PPPoE packet sent by anEthernet BAS device into a PPPoA packet and sending the PPPoA packet tothe PPPoA terminal. The conversion functional module, when determiningthat the received packet sent by a terminal is a PPPoA packet, convertsthe PPPoA packet into a PPPoE packet and sends the PPPoE packet to theEthernet BAS device; and after receiving a PPPoE packet sent by theEthernet BAS device, if determining that the terminal to receive thedata in the PPPoE packet is a PPPoA terminal according to the MACaddress, the convertsion functional module converts the PPPoE packetinto a PPPoA packet and sends the PPPoA packet to the PPPoA terminal.The conversion functional module may be a separate entity, or integratedwith the existing switching functional module or the main controlfunctional module.

In an embodiment of the present invention, the conversion functionalmodule is set in the switching functional module of the IP DSLAM device,which enables the IP DSLAM device to perform an automatic conversionbetween the PPPoA packet and the PPPoE packet and to cooperate with astandard Ethernet BAS device to enable the PPPoA terminal to access abroadband network via the IP DSLAM device. The IP DSLAM device convertsthe PPPoA packet sent by the PPPoA terminal into the PPPoE packet andsends the PPPoE packet to the Ethernet BAS device, and converts thePPPoE packet sent by the Ethernet BAS device into the PPPoA packet andsends the PPPoA packet to the PPPoA terminal. Additionally, abnormallogoff of the PPPoA terminal can be detected with an effective method inthe implementing procedure in accordance with an embodiment of thepresent invention. The method to detect the abnormal logoff of a PPPoAterminal guarantees inter-working of the protocols. Therefore, thefunction of PPPoA access can be supported properly on the IP DSLAMdevice.

Though the present invention has been illustrated and described byreferring to some preferred embodiments of the present invention, thoseskilled in the art should understand that various changes may be made inform and detail without departing from the spirit and the scope of thepresent invention and therefore should be covered in the protectionscope of the present invention defined by the appended claims and itsequivalents.

1. An accessing method for supporting a Point to Point Protocol overAsynchronous Transfer Mode (PPPoA) terminal to a broadband access devicebased on an Internet Protocol (IP) architecture, comprising: assigning,by the broadband access device, a Media Access Control (MAC) address tothe PPPoA terminal; setting up a Point to Point Protocol over Ethernet(PPPoE) connection between the broadband access device and a BroadbandAccess Server (BAS), and acquiring, by the broadband access device, aSession ID assigned by the BAS; converting, by the broadband accessdevice, a PPPoA packet sent by the PPPoA terminal into a PPPoE packetand sending the converted PPPoE packet to the BAS; converting, by thebroadband access device, a PPPoE packet sent by the BAS into a PPPoApacket and sending the PPPoA packet to the PPPoA terminal, according tothe MAC address and the Session ID; upon detecting a logoff of the PPPoAterminal, the broadband access device instructing the BAS to remove thePPPoE connection; upon receiving the instruction of removing the PPPoEconnection, the BAS removing the PPPoE connection between the BAS andthe broadband access device, wherein said detecting a logoff of thePPPoA terminal comprises: counting the number of keep alive packetsbetween the PPPoA terminal and the BAS within a pre-configured time, anddetermining whether the number increases, if the number increases,determining that the PPPoA terminal is online; if the number does notincrease, determining that the PPPoA terminal has logged off.
 2. Themethod according to claim 1, wherein a MAC address pool is configuredfor the PPPoA terminal in the broadband access device, said assigning aMAC address to the PPPoA terminal comprises: assigning, by the broadbandaccess device, a MAC address to the PPPoA terminal from the configuredMAC address pool.
 3. The method according to claim 2, wherein saidassigning a MAC address to the PPPoA terminal comprises: designating aMAC address for the PPPoA terminal statically, or assigning a MACaddress to the PPPoA terminal dynamically.
 4. The method according toclaim 1, wherein one MAC address corresponds to at least one PPPoAterminal.
 5. The method according to claim 1, wherein said converting aPPPoA packet sent by the PPPoA terminal into a PPPoE packet comprises:terminating the PPPoA packet, analyzing the PPPoA packet to get a PPPload, generating a PPPoE packet header according to the Session ID, PPPload length and related information, and encapsulating the PPPoE packetheader and the PPP load into the PPPoE packet.
 6. The method accordingto claim 1, wherein said converting a PPPoE packet sent by the BAS intoa PPPoA packet comprises: analyzing the PPPoE packet to get the PPPload, regenerating a Permanent Virtual Circuit (PVC), a port number anda slot number corresponding to the PPPoA terminal according to theSession ID, the MAC address and a Virtual Local Area Network (VLAN)identifier in the PPPoE packet, and encapsulating the PPP load and therelated information into the PPPoA packet.
 7. The method according toclaim 6, wherein the broadband access device determines that theterminal is a PPPoA terminal according to the MAC address or the VLANidentifier.
 8. The method according to claim 1, wherein if one MACaddress corresponds to one PPPoA terminal, said sending the PPPoA packetto the PPPoA terminal comprises: sending the PPPoA packet to the PPPoAterminal corresponding to the MAC address; if one MAC addresscorresponds to more than one PPPoA terminal, said sending the PPPoApacket to the PPPoA terminal comprises: sending the PPPoA packet to thePPPoA terminal corresponding to the MAC address and the Session ID orcorresponding to the Session ID.
 9. The method according to claim 1,further comprising: upon receiving a logoff request sent by the PPPoAterminal, sending the logoff request, the broadband access device;removing a PPP connection between the BAS and the PPPoA terminal as wellas the PPPoE connection between the BAS and the broadband access device,by the BAS.
 10. The method according to claim 9, wherein after thebroadband access device sends the logoff request to the BAS, thebroadband access device returns the MAC address assigned to the PPPoAterminal to the MAC address pool.
 11. The method according to Claim 1,wherein after the broadband access device instructs the BAS to removethe PPPoE connection, the broadband access device returns the MACaddress assigned to the PPPoA terminal to the MAC address pool.
 12. Anaccessing device for supporting a Point to Point Protocol overAsynchronous Transfer Mode (PPPoA) terminal, comprising: a main controlfunctional hardware module, a switching functional hardware module, asubscriber interface functional hardware module and a backplanefunctional hardware module, and a conversion functional hardware module,used for converting a PPPoA packet sent by a PPPoA terminal into a Pointto Point Protocol over Ethernet (PPPoE) packet and sending the PPPoEpacket to an Ethernet Broadband Access Server (BAS) device, as well asconverting a PPPoE packet sent by an Ethernet BAS device into a PPPoApacket and sending the PPPoA packet to a PPPoA terminal; upon detectinga logoff of the PPPoA terminal, the broadband access device instructingthe BAS to remove the PPPoE connection; wherein said detecting a logoffof the PPPoA terminal comprises: counting the number of keep alivepackets between the PPPoA terminal and the BAS within a pre-configuredtime, and determining whether the number increases, if the numberincreases, determining that the PPPoA terminal is online; if the numberdoes not increase, determining that the PPPoA terminal has logged off.13. An accessing system for supporting a Point to Point Protocol overAsynchronous Transfer Mode (PPPoA) terminal, comprises an InternetProtocol (IP) architecture based broadband access device and a BroadbandAccess Server (BAS); the broadband access device is used for assigning aMedia Access Control (MAC) address to a PPPoA terminal, setting up aPoint to Point Protocol over Ethernet (PPPoE) connection between the BASand itself, converting a PPPoA packet sent by the PPPoA terminal into aPPPoE packet and sending the converted PPPoE packet to the BAS, andconverting a PPPoE packet sent by the BAS into a PPPoA packet andsending the PPPoA packet to the PPPoA terminal, according to the MACaddress and a session ID; counting the number of keep alive packetsbetween the PPPoA terminal and the BAS within a pre-configured time, anddetermining whether the number increases, if the number increases,determining that the PPPoA terminal is online; if the number does notincrease, determining that the PPPoA terminal has logged off; upondetecting a logoff of the PPPoA terminal, the broadband access deviceinstructing the BAS to remove the PPPoE connection; the BAS is used forassigning the session ID to the broadband access device, upon receivingthe instruction of removing the PPPoE connection, the BAS removing thePPPoE connection between the BAS and the broadband access device. 14.The system according to claim 13, wherein the broadband access deviceterminates the PPPoA packet, analyzes the PPPoA packet to get a PPPload, generates a PPPoE packet header according to the Session ID, PPPload length and related information, and encapsulates the PPPoE packetheader and the PPP load into the PPPoE packet.
 15. The system accordingto claim 13, wherein, the broadband access device analyzes the PPPoEpacket to get a PPP load, regenerates a Permanent Virtual Circuit (PVC),a port number and a slot number corresponding to the PPPoA terminalaccording to the Session ID, the MAC address and a Virtual Local AreaNetwork (VLAN) identifier in the PPPoE packet, and encapsulates the PPPload and the related information into the PPPoA packet.
 16. The systemaccording to claim 13, wherein the broadband access device is furtherused for sending a notification of removing the PPPoE connection betweenthe broadband access device and the BAS when detecting a logoff of thePPPoA terminal.
 17. The system according to claim 13, wherein the BAS isfurther used for removing the PPPoE connection between the BAS and thebroadband access device after receiving the notification of removing thePPPoE connection from the broadband access device.